Plaster cast cutting machine



NOV. 24, 1953 MERKUR 2,659,969

PLASTER CAST CUTTING MACHINE Filed April 15, 1950 Patented Nov. 24, 1953 PLASTER CAST CUTTING MACHINE Martin Merkur, New York, N. Y.,assignor of onethird to Arnold Neustadter, New York, N. Y.

Application April 15, 1950, Serial No. 156,117

4 Claims.

This invention relates to a plaster cast cutting machine.

The machine which is herein described and claimed has been designedprincipally for use in cutting plaster casts of the type employed inbone fractures and similar conditions. The machine is not limited,however, to plaster cast work, and it may be utilized in many operationsin many fields and industries which have no relation whatsoever tosurgery. For example, the present machine is well adapted to cutlaminated material, such as laminated paper, wood or plastics and it isequally well adapted to cut sheet material such as paper, rubber orcloth, piled layer upon layer. And similarly, the machine may also beutilized for the purpose of cutting relatively solid material such asplaster of Paris, wood or plastics. For the purposes of the presentapplication, however, the invention will be described solely in terms ofits use in surgery,

but this will be done solely for purposes of convenience andillustration and not by way of limitation.

The manner in which plaster casts are now removed from the patient, iscrude and cruel in the extreme. Hammer and chisel are used to chip andbreak the cast and enormous shears are also employed in an effort to cutthe material of which the cast is made. There is not always sufficientroom between the cast and the patients skin to accommodate the shears,especially where the tissues are swollen. In consequence considerableinjury and pain result from efiorts to force the shears underneath theplaster cast. An indication of how diificult it is at the present timeto remove a sizable cast from a patient'may be The present invention wasborn of just such experiences in American service hospitals during thelast war.

Plaster casts are not normally placed directly against the skin of thepatient. Instead a layer or layers of absorbent cotton and/or gauze areinterposed between the patients body and the plaster cast. The plasteradheres to, and in part permeates, the cotton or gauze on which it isplaced and so it is insuificient, when removing the plaster cast, toprovide plaster chopping or enough that means be provided for cutting"or chopping the plaster and for cutting the cotton or gauze: it is atleast equally important to providemeans for adequately guiding andcontrolling cutting means and to prevent the cutting means from injuringthe patients body.

It is accordingly the principal object of this invention to provide aplaster cast cutter which:

a. Cuts both the plaster and the cotton or gauze which lies below theplaster,

b. is extremely easy to guide and control, and

0. includes means for preventing injury to the patients body.

More specifically, the plaster cast cutter constituting the presentinvention, provides means for sawing the plaster and for cutting orshearing the cotton or gauze. Still more specifically, the presentinvention provides a pair of reciprocating saw blades, each of Whichprovides its own sawing action, both blades cooperating with each otherto provide a cutting or shearing action between them.- The two bladesare mounted side by side, in abutment with each other. The cuttingaction of one of the saws is directed downwardly and the cutting actionof the other saw is directed upwardly. Since the two saws move inopposite directions at the same time, one of the saws will tend to pullthe entire cutting mechanism away from the patients body and the othersaw will tend to pull the entire cutting mechanism toward the patientsbody. These two pullingforces will neutralize each other and nounbalanced forces will be set up which the operator of the device willbe unable to control. Hence, it will be found extremely easy to manageand guide the present device.

It has above been stated that each saw provides its own cutting orsawing action and that the two saws provide a cutting or shearing actionbetween them. That each saw will provide its own sawing action, isclear. The shearing action takes place by reason of the inter-actionbetween the cutting teeth of the two saws. These teeth are not ofisetfrom each other as is the case with conventional saw blades instead theyare flush with at least one side wall of the blade proper and when thetwo blades are held side by side in abutment with each other, thecutting teeth of each blade will coact with the cutting teeth of theother blade to provide a shearing action and more particularly, aplurality of shearing actions, determined by the number of teeth in thetwo blades and by the number of times i the p absolutely certain thatthe cutter will attack the plaster cast and its underlying padding onlya nd not the patient who wears the cast. 'This'stop Fig. 5 is aperspective view of the two saw blades which the plaster cast cutteremploys.

Fig. 6 is an enlarged sectional view taken across the two saw bladeswhen they are mounted in the cutter, showing their tapered sides.

Fig. '7 is a longitudinal section through a presser foot construction bywhich the plaster cast is held steady during the cutting operation.

.Th a te eeht el i es {th i h enti h which is shown in the drawingincludes a motor housing 3 l; 0 which has an electric motor mountedtherein,

together with a suitable gear arrangement, either for-speed reducing orspeed increasing purposes,

member or guide is also adapted to prevent the,

saws and their bearing supports frjrgg'rn the patients skin. The sawingaction proceeds at a high rate of speed and considerable'rric tion andheat are thereby generated. {Ifne member or guide is completely separatefrom the and thei hea in support and h hee the he? w h th eut ihs qne aten gene ates. .i t transmitt d or eeh he ed :thr l e he s e methl eerehid 9. .the etiehtfsbedy- Th memh e guide h e th st l .a eth U-Q...It .ptex es a w deth sheet whe th p aste eas .7 y spee in eel e e them lev eh is ehd t brin t en; to \eaeem h w t the sews .1 s. o eeur e s..eeeieh true 9 t e adshh the the l te i se f may e 1 hflei e t9 yi ld ith s mann r- The P dev se rend r .h ss h e t9 see ih est r ss eh tihe,ep tiehseh a ti t esw h a Well he e t ran and of action of theprimitivecutting means and methe ls hseee d eti ed y- F exemhle, th the. time whea P as er as eeeme un u tabl er e ht hhe a i atio t e e et eh b of edued sw ing in t l wh ch i encloses, Presentrnethods require that theplaste ees ihe e ve fro},n t e l mb ies ro ee, an hat s new la te eas erep ed h reon- Ihe pr ent de ee r n t Pos bl to s e th e d'e'esth im lyutt n a s ri est hi an 'the 'fi tih i t th s elling edu d mhs e sehe s hby me t P e e detie to increase thecom-fort of patients whose trunk iscompletely encased by means of a plaster east. Suchp'atients sufferintensely, especially in warm T4951 hu i We he s n e t e is n wa t th prnt e eh nhe er a l i ing the ehs l sheetin and ir t ti g e si- 12.3. .5w. are e esiiby p spiration en hee hhsl t th the a As de 'i em t dis omor w ch is ther b eau ed r he nd skin intest hc ht riamyresmt. h resentdev e eh- .dier it p ss ble. i the i t al a d of suit ble l. tef t wndows nt th p a er ea t ithout weakening it in any serious orsubstantial respect, for the purpose of providing adequate ventilationand also to provide access to' the patients body, for cleaning purposes,sponging it with alcohol and other important purposes.

A prefer-red torm of this invention is shown ibyawayof illustration inthe accompanyingdrawing in which Fig. 1 is a side View of the plastercast cutter herein claimed, showing the plaster cast and its'lllldenlying padding in section.

; Fi;g. 2 is a-front .viemv of said plaster .cast cutter its e er I XBQYG t r from to expo i P P rts, ;i$.fl Q 3 tl1: 3h seetieh en the l ne.373

as.giesired or required, or simply for drive transng -issig n .punpo seswithout either an increase or a decrease in speed. Extending forwardlyfrom lsaid housingisadrive shaft I I which is connected ,sepratihleitheic s a Wheelie r rhth ;.1oe tieh e e ehh pi 3.

V and Zia tp thegears inside the motor housing. It is this drive shaftwhich operates the mechanism hereina te eset hee. Ah eleett erd L2 s veonected to the motor in the usual manner. Also fas ened te t e mete h inis h h l e 1 Wh eh th eu te m e held i the and she gpenatetl. A switch14 which is located on. the ente h in unde h he l eeh el the motor eirtcu-it. {Ifhe operating mechanism of the present device is located infrontof the motor- -hous i ngand acover I 5 is provided to enclose said"mechanism.

of the operating mechanism of this device is a pair of crank wheels 21'}and 2i respectively; which aot uate a pair of connecting rods 22 and :23respectively, which, in turn, are c on;nected to, andajctuatefa pair oflongitudinally movablerods gfl and '2-5 respectively. Saw blades 3,9andsl are connected to rods '24 and 213 and when the crank wheels andconnecting rods cause said rods and- &5 to move longitudinally ofthemselves in reciprocating fashion, the saw blades are thereby cansedto engage in the same kind pf reciprocating movement. More specifically,crank wheels-2B and 2| comprise a pair-of gear wheels which are inengagement with a j'ql' ird gear wheels- 3; lrank gearwheels 2t and 2-1are mounted res p ectively'on stud shaf ts (I' l and 35 and gear wheel3-3 is mountedon drive .s efti'l'e e m ht e d- Hence wh n e meter is inoperation, gear wheel 33 will pause crank "gearw-heels 2B and?! torotate on their respec- 'tiye stud shafts, in the same direct-ion.Screws vees hh pin f teeh h elt t9 se e than sea whe l Y. y he is e 1 9.eist he cation of crank pin 3'? oncrank in spaced, parallel relationshipthereto. Slides 4&5 end-46 e e fix d t xe iproe ns rods Hand 25 and theareslide ly m unt d n sa d fixedar-od 3 and 1 4- P hsM-ehd 18 ivota ly eh e te hnectmg rods 2 2 and 23 to slides 45 and 46 and. sth e idslid s eer a h d to ee eee ns red 2 nial? t hy'means of sa d s an sa d slielesttthe ehhe tihs s are ttached to l herteeiprq atihs eds.

It will now be noted that the two bearing mmbers 40 and 4| arefastenedby means ofscrews 49 to'a housing 50 which may, or may not, be integralwith the motor housing. The drawing shows housing 50 as a separatehousing which is fastened by means of screws to the motor housing, butthis should be understood as being simply illustrative of the presentconstruction. For the purposes of the present application, however,'itwill be assumed that housing 50is'a'part of the motor housing and it isimmaterial whether the two housings are integral with each other or nut.Housing 50 has an upwardly projecting portion 52 and a downwardlyprojecting portion 53. A channel 54 is formed in the upwardly extendingportion 52 and a second channel 55 is formed in the downwardly extendingportion 53. These channels are adapted to accommodate the reciprocatingrods 24 and 25 in their respective upward and downward movements inbearings 40 and 4|. Connected to the lower end'of reciprocating rod 24is a block 58 and a similar block 59 is fastened to the lower end ofreciprocating rod 25. It is to these blocks that the saw blades areattached by means of screws 68. More specifically, it will be seen thatthe upper ends of the two saw blades are provided, respectively, withside pieces or flanges 62 and 63 which have holes 64 and 65 formedtherein. These flanges 62 and 63 are adapted to rest upon blocks 58 and59 and it is through holes 64 and 65 that screws 68 may be inserted toaffix said flanges, and hence the saws, to said blocks.Asthereciprocating rods and their respective blocks engage inreciprocating upward and downward movement, so do the saw blades engagein the same reciprocating movement.

It will be seen in Fig. 5 that the two saw blades are notinterchangeable and hence one may be described as the left saw blade,and the other as the right. The teeth of one of said blades, that isblade 30, are provided with cutting edges which face downwardly. TeethH, on the other hand, of blade 3i, have cutting edges which faceupwardly. Hence the cutting action of saw blade 30 takesplace on itsdownward stroke and thecutting action of blade 3I takes place on itsupward stroke. It will be noted in Fig. 2 that. crank pins 31 and 38 areso situated on the crank wheels, that the greatest possible leverage isbrought-to bear-upon the saw blades during the course of their cuttingstrokes. 3

. The cross sectional View of the blades which Fig.6 constitutes,discloses the fact that the two blades abut each other on theirrespective facing sides. Since the teeth of said blades, at least. alongtheir said facing sides, are not offset from each other, it will beclear that the teeth ofeach blade will slidably abut the teeth of theother blade when the two blades are caused to reciprocate relative toeach other. i A cutting action will thereby be set up between the teethof the respective blades which will cut or shear the cotton or gauzepadding 80' underneath plaster cast 8|.

If it beassumed that the cutting edges of teeth 10 face downwardly andthe cutting edges of teeth 1| face upwardly, it will be apparent thatthe cutting action will take place between the two blades only whenblade 30 moves downwardly and blade 3! moves upwardly. If desired,cutting edges may be provided on both sides of the cutting teeth of bothblades so that a cutting action will take place on the upward anddownward strokes of the two blades.

It' will also be seen in Fig. 6 that the non facing sides of the twoblades are tapered in opposite directions, that is, they converge fromtheir rela-* tivelythick teeth portions to their relatively thinbackedge portions. These tapers on the two' blades are provided for the samereason thatsaw teeth are normally offset on hand saws, that is, to cut aslightly wider groove or saw cut'into the material or work than the bodyof the blade would'require, thereby providing clearance for the body ofthe blade.

It will also be seen in Fig. 6 that the back edges 83 and 84 of blades30 and are still further tapered and that they meet virtually at apoint. These tapered back edges fit into a V-shaped groove or channelformed in a guide block 85 on apost 86. This post is fastened to housing50 immediately behind the two saw blades andits thickness correspondsapproximately to the combined thicknesses of said two saw blades. At thebottom of column 86 is a bifurcated foot 81 which straddles the twoblades and helps prevent them from bending or spreading apart. Block 85performs the same function since its V-shaped channel tends to cam orwedge the two blades together and the harder the blades are pressedagainst the work, the more tightly will said block 85 hold the twoblades together. -In other words, block 85 serves as a guide or trackfor the two saw blades, holding them in close abutment with each otherand bracing them against rearward bending or yielding when they arepushed hard against the work.

A second column 90 is afiixed to housing 50. behind, and in spaced,parallel relation to column 86. This column 90 has a foot 9| whichextends forwardly and belowfoot 81. At its forward end it is bentupwardly and backwardly to form'a wedge or ramp 92. Foot 9| constitutesa guide or stop member which restsagainst the body'of the patient toprevent the saw blades from injuring him. Since foot 9| and column 90'whichsupports it are separate 'and apart from column;

86, block 85 and foot 81, said foot will remain. relatively cool eventhough said blades, block,, and foot 81 may become exceedingly hotduring,- the course of the cutting operation. Wedge on ramp 92 will liftthe work to the level of foot 81! to enable the blades to enter intocutting engagement with said work. See Fig. '1. This wedge or ramp willalso serve as the means of spacing the plaster cast and the paddingwhich lies below it, from the body 96 of the patient.

Referring now to Fig. 7 it will be noted that a spring-urged presserfoot may be employed to press down upon the plaster cast to hold itsteady and to reduce vibrations during the cutting operation. Thepresser foot construction includes a casing l5a which is adapted to bemounted upon casing or cover member [5 by means of the same screws whichhold said cover or casing member to the main casing or housing or thedevice. Casing member [5a comprises a tubular housing 95 having ears orlugs Ill formed thereon and holes H2 formed in said ears or lugs. It isthrough these holes that screws H3 may be inserted in order to fastencasing member l5a to casing memher [5, and both of said casing membersto the main casing of the device. Housing 95 has a cylindrical hole 96formed therein longitudinally thereof. A piston-like member I 04 isslidably mounted in said cylindrical hole and it will-benoted that a setscrew I05 is fastened thereto and that said set screw rides in alongitudinal slot I06 formed in the wall of said tubular housing 95.This screw-in-slot construction enables the piston-like member 104 tomove longitudinally- 7 in the-cylindrical hole, but it ipreventsrotar'ymovement of said piston like member insaid hole; Also screw I95 servesas a stop member whichlimits the longitudinal stroke of the pistonlikemember I04 to the length of slot III-6, less the diameter of said screw.Connected to the top of piston-like member I94 is 'a stem III'I whichprojects upwardly through'a hole III! in an 'ex-' ternally threadedbushing 198. This bushing is screw threaded into tubular housing 95 andit has a knurled head I09 so that'i-t may be adjusted in said tubularhousing. :A compression spring 98 is mounted in cylindrical hole 96 andripen stein II'II. Its upper end bears against threaded bush ihg I98 andits lower end bears "against piston like member I94. This arrangement ofparts tends t6 urge the piston-sure member I94 down wardlt as far as itsscrew I05 in slot I96 will allow it te g6. The tension bf the springniaybead justed by simply turning knurled head I09 of threaded bushing I98.V

A presser foot I9 0 is rotatablyfastened to the lower end of piston likemember I04. This presser foot is a button-shaped member which is convexon its lower surface. It is this surface which makes contact with theplaster cast and holds theplaster cast firm against foot 9I abovedescribed, More specifically, it is the tension of spring 98 which holdsthe presser foot against the plaster cast and holds the plaster castagainst ramp 92 of foot 9I. Presser foot I00 has a cylindrieal boss 99projecting upwardly therefrom and into a correspondingly shaped holeformed in piston-like member I04. A screw -IM, whose head lodges in arecess I92 in the bottom of the presser foot, extends through anaxialhole in the presser foot and in boss 99 and into a threaded h'ole I03 rormedin piston-like member I94. It is by this-means that the presserfoot is rotatably mounted in the lower end of the piston-like memberI94. Although screw IOI is tight in its said threaded hole I93, it isrelatively loose in presser foot I00 to enable said presser foot toswivel or rotate about it.

;It will be understood from the foregoing that what is shown in thedrawing and what has above been described in detail is simply onepreferred form of the invention. This preferred form may be modified inmany ways and other forms may be provided, all within the broad scopeand eoverage of the invention. For example, the drive mechanism whichaccommodates 'the two saw blades is merely illustrative of the manykinds of driving mechanisms which may be employed to cause the twoblades to move alternately up wardly and downwardly, in oppositedirections. The specific type of saw blade which is shown in the drawingis also purely illustrative of the many diirerent kinds of saw blades,and even files, which may be used in 'eonne'cti'on with the presentinvention. Nor need the saw blades be of the reciprocating type.Circular blades driven in opposite directions would also perform well.

I claim:

1; A portable power-driven cutting machine comprising, in combination, amotor housing, an elongated guide member having a v grooved bladesupport rigidly extending from said housing, a pair of recipr'oeablecutting blades sli'dably mounted side by side in the groove of saidsupport, thecutting edges of said blades being wider than said support,the back edges of said blades being tapered to fit into the groove ofsaid support, a guard member rigidly attached to said housing andextending therefrom parallel to but spaced from said guide, said guardmember underlying the ends of said blades-opposite from said hous= ing,and motor-driven means in said housing for oppositely reciprocating saidblades.

2. A portable power-driven cutting machine comprising, in combination,a'motor housing, an elongated guide member having a V -gro'oved bladesupport rigidly extending from said hous ing, a pair of reciprocablecutting blades slidably mounted side by side in the groove "of saidsupport,- the cutting edges of said blades being wider than saidsupport, the back edges of said blades being tapered to fit into thegroove of said support, a guard member rigidly attached to said housingand extending therefrom parallel to but spaced from said guide, saidguard member underlying the ends of said blades opposite from saidhousing, motor-driven means in said housing for oppositely reciprocatingsaid blades, and vertically yieldable work' h'olding means adjacent tobut disengaged fromthe cutting edges of said cutting blades, saidwork-holding means normally extending toward the ends of said bladesopposite from said housing.

3. A portable power driven cutting machine comprising, in combination, amotor housing, an elongated guide member having a V'-grooved bladesupport rigidly extending from said housing, a pair of reciprocablecutting blades slidabl y mounted side by side in the groove of saidsupport, the cutting edges 'of said blades being wider than saidsupport, the back edges of said blades being tapered to fit into thegroove of said support, a guard member rigidly attached to said housingand extending therefrom parallel to but spaced from said guide, saidguard member underlying the ends of said bladesopposite from saidhousing, motor-driven means iii-said housing for-oppositelyreciprocatingsaid blades, work'- holding means slidably mounted on said housingadjacent to saiu cutting blades, and an adjustable compression springnormally biasing said workhoming means downwardly toward the ends ofsaid blades opposite t6 said housing.

4. A portable powerydriven cutting machine comprising, in combination, amotor housing, an elongated guide rneinber having a V'-grooved bladesupport rigidly extending from said hous= ing, a pair of reciprocablecutting blades sl idably mounted side by side in the groove of saidsupport, the cutting edges of said blades being wider than said support,the back edges of said blades being tapered to fit into the groove ofsaid support, a guard member rigidly attachedto said housing andextending therefrom parallel to but spaced from said guide, said guardmember underlying the ends of said blades opposite from said housing,motor-driven means in said housing for oppositely reciprocating saidblades, and a spring-"loaded piston sli'dable along an axis parallel tosaid cutting blades and adapted to engage material to be out betweenoneend of said piston and said rigidly attached guard member.

MARTJ'IN

